Thermostat.



No.1740,254. PATENTED SEPT. 29., 19,03.

. L. H. DES ISLES.

THERMOSTAT. APPLIOATION FILED 1111.19, 1901.

I0 MODEL.-

Patented September 29, 19015.;

UNITEDSTATESMPAIENT Curiel-3.

LEONARD ll. DES SLES, OF CAMBRIDGE, MASSACHUSETTS.

THERMOSTAT.

SPECIFICATION forming part of Letters Patent No. 740,254, dated September 29, 1903;

Application filed January 19, 1901. Serial No. 43g892. (No model.)

To all whom it may concern:

Be it known that I, LEONARD H. DES IsLEs, a citizen of the United States, residing at Cambridge, in the county of Middlesex, State of Massachusetts, have invented a certain new and useful Improvement in Thermostats, of which the following is a specification, reference being had therein to the accompanying drawings.

The invention relates to thermostats or thermally-operated instruments, and particularly v to that class of thermostats wherein an electric circuit is made or broken, as the case may be, upon the occurrence of such an increase in the temperature ofthe surrounding atmosphere as accompanies a tire.

More especially, the invention relates to the kind of thermostat in which the mechanism employed is held normallyinactive by means of a solder-joint and is caused to act by the melting of the solder. Some features of my device, however, are equally applicable to other forms of thermostat.

Commercial solder of a permanent character melts at about lo()o Fahrenheit; but hitherto it has been found impracticable to construct a thermostat depending for its operation upon a solder-joint which can be relied upon to act until the rising temperature has considerably exceeded the melting-point of the solder. been met in the construction of a thermostat, relatingto economy of manufacture and the prevention of deterioration of the instrument when in position a long while without being actuated. V p

The principal aim of the present invention is to produce a thermostat whose test-point of action will closely approximate the minimum temperature named above.

Another object is to decrease the liability of the efficiency of the instrument being diminished or destroyed.

A further design is to protect the parts of the instrument'from laccess of moisture.

Other points of improvement will appear in the following paragraphs, and it will be obvious that several of these are applicable to electric alarms in general, Whether or not they are thermally operated.

.The improvement will first be described in Other practical difficulties have projections 5.

connection with the accompanying drawings,l which illustrate the best embodiment of the device thus far contrived, and afterward the features of the invention will be particularly pointed out, and distinctly defined in the claims at the close of this specification.

In the drawings, Figure l is a plan view of the cap of the thermostat seen from the open back thereof. Figr2 is a section on the line 2 2 of Fig. l looking in the direction indicated by the arrows at the extremities of that line and showing the base-plate on which the cap is supported. Fig. 3 is a similar section on the line 3 3 of Fig. l. Fig. 4 is a sectional view of the assembled parts that are united by the solder-joint.

The terminals of the electric circuit in which the thermostat is placed are inclosed between a base-plate l and a cover 2, both of these parts preferably being made of porcelain. The base-plate has an upturned rim 3, and the edge of the cover fits Within this rim and makes contact with the inner surface of the base-plate. lIn order to attach the instrument to a fixed support, such as a Wall or ceiling, screws 4 are employed. The base-plate is provided with circular projections 5, the ends of which abut against the cover. Holes are formed through the cover, projections, and base-plate to receive the said screws.

.Rims or beads 6 are formed on the inner surface of the cover, surrounding the ends of the By this construction it is insured that any moisture seeking escape along the screws shall be prevented from reaching the working parts of the instrument.

Hollow plugs 7 are slipped upon the screws prior to the introduction of the latter into place, the screw-heads thus being caused to remain elevated some little distance above the surface of the cover, whereby the central portion of the cover is protected when the thermostat is located in any exposed position of use, and consequently the heat-affected element of the instrument, which occupies such central position, is prevented from becoming injured. the screws 4 in this office are the bindingposts 8, which occupyintermediate positions with relation to the screws.

inasmuch as the thermostat is frequently Cooperating with IOO hung upon a free circuit-Wire independently of a fixed support, it becomes desirable to attach together the base-plate and cover independently of their joint attachment to such fixed support, and for this purpose the binding-posts are utilized to furnish a bearing for such attachment, the Shanks 10 of the binding-posts being extended through the baseplate and their extremities being screwthreaded and provided with nuts 12, which set in recesses 18 in the rear face of the baseplate. The binding-posts have squared enlargements 8l at the base of their shanks, which set in squared recesses 82 in the outer face of the cover. By this means the binding-posts are prevented from turning when the binding-screws are tightened and loosened, a contingency in which they Would loosen the nuts 12 and permit of the separation of the cover from the base-plate.

One of the terminals of the circuit through the thermostat is a plate 9, through which passes the shank of the corresponding binding-post. In the operation of assembling the parts of the instrument a nut 11 is placed upon the said shank for the purpose of clamping the plate iirmly to the cover. A portion 131 of the plate v9 is bent upward obliquely to aord a contact-surface for the second terminal. The second terminal is a blade-spring 14, connected with the second binding-post and clamped to the cover by a nut 15 on the shank of the binding-post in like manner to the plate 9. The spring 14, however, is not arranged in the customary manner-that is, extending directly across the space within the cover toward the plate 9but starts outward and then doubles on itself and extends into proximity to the said plate. Thus there is obtained a very long spring which, because of its length, requires to be subjected to very little angularI deflection in order to separate its extremity the required distance from the surface of the fixed terminal With which it coacts. A comparatively short spring like those commonly in use which is constantly maintained in a position of considerable deflection requires to he made of thin steel or some similar metal and is apt to rust in a moist atmosphere and become weakened or destroyed. Along spring, on the other hand, which is subject to only slight angular deflection,maybe madeofcomparativelythick metal of atypepossessinga moderate degree of resiliency and not likely to become rusted. I have obtained excellent results by constructing the spring in question of phosphor-bronze.

A coating 84 of non-corrodible material is applied to the contacting portion of the terminal 14, and a similar coating S5 is applied to the terminal 131 in order to insure a perfect contact being made when the instrument is caused to act. In practice these coatings arer constituted of solder, which not only is non-corrodible, but operates to melt When the two terminals are brought together, the coatings thereby fusing together and forming a perfectly continuous bridge from one terminal to the other. This will occur although particles of dust or other foreign matter should have lodged upon either of the terminals which in the ordinary construction would prevent the passage of the electric current.

In the construction herein shown, as has already been explained, the Shanks of the binding-posts pass through the interior space of the cover. Consequently the coacting portions of the terminals require to be offset from the portions thereof which surround the said shanks and which are clamped to the cover by the nuts 14 and l5. In other cases, however, it may not be found necessary thus to offset the terminals.

I have made experiments with a View to devisinga construction embodying asolder-joint that shall operate at a temperature only slightly exceeding the melting-point of the solder employed. The conditions present in a small and more or less delicate instrument of the class under consideration are somewhat un usual. The parts temporarily united by the solder-joint are necessarily under some degree ofstress tending to separate them from each other; but it is desirable that such stress shall not be excessive, and it is essential that the device shall act absolutely Without fail. It is also obvious that in spite of precautions taken to prevent the entrance of d ustinto the interior of the instrument there are certain unfavorable positions of use in which such entrance may occur. The dust may in time accumulate to so considerable a degree as to clog the mechanism and decrease the operative stress just mentioned. It is essential that the thermostat should act even under this adverse condition.

In the course of investigation I have found that when tWo metal plates are arranged face to face with afilm of solder between them, forming a solder-joint, and this combination of parts is heated in a test-oven the metal plates separate at an earlier point of time when subjected to a moderate stress in the plane of their approximately contiguous surfaces than they do under the same stress applied in a direction normal to that plane. In other Words, such metal plates slide apart sooner than they pull apart. I have further found that a very advantageous form for such metal plates is that of tubes, one of which is slightly smaller in diameter than the other, so as to slip into it with just clearance enough for the introduction of melted solder between the latter, forming an annular film or zone, adhering when cool to both of the tubes and preventing them from sliding or slipping upon each other. Such vtubular form affords the maximum of strength and area of the metal pieces with the minimum of thickness thereof. A furtherstep consists in closing the end of one ofthe tubes and utilizing the closed end as a bearing for the actuating part of the in- IIO strument which is to be normally held from motion, but released upon the melting of the solder-joint. The said closed end also admits of the use of a very thin tube by assisting in stiffening the same.

In carrying the foregoing conceptions into effect I have arranged the instrument as follows: A central aperture is formed inthe cap 2 to receive a sleeve 16 of hard rubber. The inner end of the sleeve has an outwardlyturned flange 161 abutting against the in terior rim of the aperture. The body of the sleeve projects outward through the aperture. The outer end of the sleeve has an inwardly-turned iiang'e 162. A thin metal tube 17 constitutes one of the two parts between which the solder-joint is formed. The tube 17 has an outwardly-turned flange 171 at its base,which overlies the flange 162 of the sleeve 1G and retains the tube within the sleeve, and a brass or other metal ring 172 is slipped upon the tube to strengthen the flange 171, inasmuch as the tube is likely to make a somewhat loose t in the sleeve and is made of such thin material that the said flange might give enough to allow the tube to become disengaged from the sleeve. Within the outer,

end of the tube is placed a slightly smaller tube 18, closed at its outer end, which may conveniently be termed 'a cap and which constitutes the second of the two parts of the solder-joint. 19 designates the annular film or zone of solder between the tube and cap. After assembling the tube, ring, and cap it is found most convenient to introduce the nlm of solder between the tube and cap by dipping the assembled parts into a receptacle of melted solder, and thereby applying a complete coating to them. In this way they are completely protected from corroding without the sensitiveness of the instrument being in any degree decreased. The sleeve 16 serves to support the tube 17 and to insulate it thermally, so as to minimize dissipation of heat; but obviously in some cases the whole cover 2 might be formed of hard rubber, and there would then be no necessity for the use of the separate rubber sleeve.

A retaining disk or saucer 21 is attached to the under surface of the spring-terminal 14, and a spiral spring 22 is introduced, which takes bearing at its upper end against the saucer 21 and at its lower end against the closed end of the cap 18. The spiral spring is arranged to force the spring-terminal out of electrical contact with the fixed terminal and into supporting contact with the baseplate. The parts are so proportioned that only a slight degree of motion is required in order to bring the spring-terminal into this latter position, and thus onlya moderate degree of angular deflection can by any possibility occur. The spiral spring 22 may be made stronger than is necessary to displace the spring-terminal into its position against the base-plate, so as to insure the forcing out of the cap 18 when the zone 19 of solder melts. Thus the instrument is maintained in its normal inactive state ,so long as the cap 1S and tube 17 are united by the interposed film of solder.

A The described construction, as has already been implied, affords the necessary strength of the parts that are united by the solderjoint, while permitting them to be formed from very thin metal. Hence the heat that actuates the device has the most immediate access to the nlm of solder and the least opportunity of dissipation through surrounding-parts. When the solder melts and the cap is forced out of the tube by the pressure of the spiral spring, it will be seen that the movement of the cap is from a relatively cool part of the tube to a relatively hot part thereof, and there is therefore no tendency for the solder to resolidify to any degree and so retard the complete and immediate escape of the cap.

Only a very small amountof solder, which is relatively an expensive material, is required in the device as thus constructed. The tubes and caps may be cheaply made and easily assembled in large quantities.

I make no claim herein to the combination, in athermostat, of means of support, terminals thereon= thermally-released mechanism normally operative to hold the terminals separated from each other, means to bring the terminals into contact with each other, and a coating fusible in the presence of abnormal heat applied to the contact portions o the terminals.

What I claim is- 1. In an electric alarm, the combination 0f a base-plate, a cover, b inding-posts mounted on the cover, and shanks for such bindingposts passing through the base-plate and provided with nuts to hold the base-plate and cover together,

2. In an electric alarm, the combination of a base-plate, a cover, projections on lthe baseplate making contact with the cover, the said base-plate, projections, and cover being provided with holes therethrough, and screws passing through such holes to attach the instrument to a fixed support.

3. In an electric alarm the combination of a base-plate, a cover, a thermal device projecting from the cover, screws passing through the base-plate and cover to attach `the instrument to any suitable'support, and hollow plugs upon the screws to elevate the screwheads above the surface of the cover and thereby protect the thermal device from injury.

a base-plate, a thermal device projecting therefrom, screws passing through the base'- plate to attach the instrument to any suitable support, and hollow plugs upon the screws to elevate the screw-heads above t-he thermal device and thereby protect the latter from injury. i 5. In an electric alarm, the combination of 4. In an electric alarm, the combination of IOO IIO

a base-plate, a cover, projections on the baseplate making contact with the cover, the said base plate, projections, and cover having holes therethrough, screws passing through such holes to attach the thermostat to a xed support, and a raised rim on the cover, surrounding the projections.

6. In a thermostat, the combination of a means of support, a terminal mounted thereon, a second terminal movable into contact with the first, and spring-pressed to tend to cause such movement, a fixed metal tube, a metal cap fitting the tube and united thereto by solder, and a connection between the cap and the spring-pressed terminal whereby the pressure of the said terminal constantly tends to separate the cap from the tube and operates to do so upon the solder becoming melted.

7. In an electric alarm, the combination of a base-plate, a cover, a spring-terminal mounted on the base-plate, a second terminal cooperating therewith, a thermally-released element supported by the cover, and a spring interposed between the latter element and the spring-terminal for holding the spring-terminal separated from its cooperating terminal and in supporting contact with the base-plate while the thermostat is set for operation.

8. In an electric alarm, the combination of a base-plate, a cover, a binding-post having a shank extending through the space between the base-plate and cover, a terminal formed integrally of spring metal having a recurved and offset end provided with an aperture to receive the said shank, and a nut on the said shank to secure the terminal in place.

9. In an electric alarm, the combination of a base-plate, a cover, binding-posts having Shanks extending through the space between the base-plate and cover, terminals consisting of plates having oppositely-oftset supporting portions through which the Shanks of the binding-posts pass, and nuts on the said Shanks to secure the said plates in place.

10. In a thermostat, the combination of operating mechanism adapted to be held normally inactive, and a thermally-operated element composed of two parts united by a solder-joint, and a coating of solder completely covering the said parts.

11. In a thermostat, the combination of a means of support, terminals thereon, a cover inclosing the terminals, a thermal device supported by the cover, connections between the thermal device and the terminals, and an intermediate thermally-insulating member interposed between the cover and the thermal device to minimize dissipation of heat from the latter to the former.

12. In a thermostat, the combination of a means of support, a terminal mounted thereon, a second terminal movable into contact with the first, but normally restrained from such movement, a fixed metal tube, a metal cap fitting the tube and united'thereto by solder, and a connection between the cap and the movable terminal including means of pressure constantly tending to separate the cap from the tube and to permit the movable terminal to make contactwiththe xed terminal, and operating to do so upon the solder becoming` melted.

In testimony whereof I affix my signature in presence of two witnesses.

LEONARD H. .DES ISLES.

Witnesses:

ROBERT WALLACE, LEPINE HALL RICE. 

